Telegraph printer



Nov. 15, 1938. L. CAMMEN i 2,136,411

TELEGRAPH PRINTER Original Filed Jan. 51, 1955 s Sheets-Sheet 1 A A IIIIIIA \\\\\\\\I JJ INVENTOR.

ATTORNEY.

Nov. 15, 1938. L. CAMMEN TELEGRAPH PRINTER 3 Sheets-Sheet 2 Original Filed Jan. 31, 1935 37 El Sk vill! I.

INVENTOR:

ATTORNEY.

Nov. 15, 1938.

L. CAMMEN TELEGRAPH PRINTER Original Filed Jan. 51, 1955 5 Sheets-Sheet 3 II F,

INVENTOR.

ATTORNEY.

tension of spring 23.

Patented Nov. 15, 1938 PATENT OFFICE TELEGRAPH PRINTER Leon Cammen, New York, N. Y., assignor to Carolyn O. Cammen, New York, N. Y.

ApplicationJanuai-y 31, 1935, Serial No. 4,241 Renewed January 22, 1938 9 Claims.

This invention refers to telegraph printers of the start-stop type and for the sake of illustration describes one operating on the so-called five impulse code, comprising a start period, five coding periods and a stop period which need not be all of the same length though the duration of the entire cycle from the instant of start of one character to the instant of stop thereof must be substantially constant. The apparatus however easily lends itself to adaptation to other codes, such as the 6-impulse code common in machines having both upper and lower case letters. I

In the illustrations,

Fig. 1 shows five permutation bars, a permit bar and a selector pin in section.

Fig. 2 shows a permutation bar and its operating mechanism.

Fig. 3 shows the printing shaft, means of starting and stopping its rotation, and the positioning of the shaft by the co-action of the selector pin and abutment on the shaft.

Fig. 4 shows the yielding motor drive.

Fig. 5 shows the electric circuit of the sender and receiver.

Fig. 6 shows a two-element selector pin.

Fig. '7 shows a timing diagram of a cycle according to E. S. Ritter.

Fig. 8 shows a medication of the timing circuit of Fig. 5.

Like many other apparatus of this kind, the present invention employs five permutation bars, differentially slotted as shown on p. 219 of H. H. Harrisons Printing Telegraph Systems and Mechanisms (Longmans, Green 8; Co., London, 1923) a maximum of 32 slots being provided, in

cooperation with thirty-two coding pins l'l, each equipped with a spring or other energy storing device I 8, acting against a limit-motion l9, and tending to forcethe pins ,I'I into the slots. This can happen to one pin in each cycle only when all five of the slots in the five bars are in line, and universal bar 56 has receded suffi'ciently to permit the pin to drop in. Printing telegraph engineers know that for every position of the five bars with respect to one other, only one pin is capable of dropping into a set of slots arranged in line to receive it.

Originally, bar I I, Fig. 2, is held in the position shown by the trigger detent 22 against the If, however, magnet 21 (which, as will be later shown, may be supplied with current over the line from the sending station) is energized, it attracts 22 and thus permits bar H to move to the right through a predetermined distance equal to one tooth space. The bar H may be moved into its original position by shifting member 24 by means to be shown hereafter, permitting the re-engagement of trigger detent 22, it being assumed of course 5 that in the meantime magnet Zlhas become deenergized. Each of the five bars is supplied with its own magnet, trigger and spring which is however merely a convenient design and not a matter of absolute necessity. No novelty is claimed for the apparatus thus far described.

The type wheel shaft 103 (Fig. 3) carries a number of abutments 102, one for each character and functional operation, so positioned that when the pin I1 is permitted to fall into the selected slot, it gets into the way of an abutment.

In its original position, shown in Fig. 1, pin I1 occupies the position 546 of Fig.3, which permits abutment I02 to pass by unimpeded. When, however, the pin has been projected into the slot in the permutation bars, it comes. to occupy position 645 in which an impingement by the abutment takes place, as shown in Fig. ,3. The abutments are distributed along the shaft so as to form substantially a one-turn helix.

The type wheel shaft is yieldingly driven by motor 30, e. g. through a spring clutch 3|, the motor running all the time and the shaft only when permitted to do so, by the mechanism. Thus the type wheel shaft cannot turn as long 0 as abutment 102 is in the co-acting relationship with pin 645 shown in Fig. 3. Provision is also made to keep the shaft stationary by means of gear or ratchet 128 rigidly attached to the type wheel shaft and stop 129 capable of engaging therewith.

As evident from Fig. 1, pin I! cannot move until all the five slots have been lined up in the I proper sequence, which is done by either keeping the bars II to IS in the positions where they are, held by the trigger detent or permitting them, or some of them, to slide to the right under the action of spring 23 after the trigger detent has been withdrawn. If the sending station transmits a marking impulse during the period when one of the magnets 2| is in the receiving position, 22 is attracted and bar ll caused to move to the right. If the impulse is a spacing one, which means that no current is flowing during that time period, the trigger is not disturbed and bar ll not moved. The slots in the bars are so arranged that the selector pins can engage with some of the slots when the bars have been moved and with some other slots when they have not been moved. The slots are therefore aligned in their operative positions some time in the fifth coding period, this being followed, first, by the motion of the permit bar It, the purpose of which is to keep pin l1 away from the bars lI-I5 while they are or may be moving to the right, to prevent interference with this motion. Permit bar i6 is moved by a can, as will be set forth in more detail hereafter.

As soon as permit bar I 6 has moved, all the pins try under the action of their springs ill to get into the slots in the permutation bars, but only one pin can do so and thus project into the path of the abutments on the type wheel shaft. Next, the same cam or a coacting cam moves the stop 129 out of engagement with ratchet I28, and it is only then that the type wheel shaft I03 can start rotating, this rotation continuing until the shaft is brought to a standstill by the abutment hitting the pin 645. This rotation may involve a little more than 10 deg. of travel, or a complete revolution, depending on the sequence of the characters, but the latter alone need be considered for purposes of design of the apparatus forming the subject of this invention.

When abutment I02 impinges on pin 645, a blow is produced, and it is obviously important to make the efiect of this blow as small as possible. The impact is a function of the kinetic energy of the rotating member, 1. e., shaft, type wheel and abutments, and varies as the square of the speed; this makes it necessary to reduce the speed of rotation as much as possible and the best way to do it is by increasing the time during which the shaft can travel.

To accomplish this, stop I29 is released as quickly as possible after the engagement of pin 645 with abutment 102, whereupon the shaft 103 carrying the type wheel is free to start spinning. The use of a friction drive, as e. g. through a spring clutch, has the advantage that very little time is lost in applying the motor power to the type wheel shaft, and that the motor is running all the time at its fullrated speed which in turn means that no time is lost in accelerating to the full speed the motor itself.

As the permutation bars I l-l5 do not have to start moving until some time in the first coding period, the type wheel shaft does not have to be stopped until then,'or for the sake of safety until the end of the start period, it being assumed that sending proceeds at such a rate as to leave only the bare unavoidable time, or. no time at all, between the end of the stop period of one cycle of transmission and the beginning of the start pe riod of the next cycle. At that time two acts are performed. In the first place, by means of a cam operated by motor power in a manner to be shown, the stop is re-engaged with ratchet 1'23 which is easy to do as the type wheel shaft is held stationary by the abutment bearing against the pin. This is an important feature as it affects favorably the life of the ratchet and stop as compared with What it is in apparatus which has no such provision and has to stop the shaft by a ratchet and pawl while it is moving at full speed.

The next thing is to free pin 645 of Fig. 3 (ll of Fig. 1) from the engagement with the permutation bars and abutment 102. It is held in the slot by the action of spring 18 which need not be very strong as all it has to do is to move the pin into the slot. Its removal is complicated by the fact that the pin is also held by its contact with the abutment, the entire force of the motor as transmitted by the spring clutch being used to hold it there. A knock-01f plate I6 is therefore provided, so timed by means of a cam as to move the pin I! (645 of Fig. 3) out of engagement with the abutment 102 which also brings it out of engagement with the slots of the permutation bars. Immediately thereupon face cam 24 is moved returning all the permutation bars into the control of the trigger detents 22.

It will be noted that the type wheel shaft remains stationary from about the beginning of the first coding period to the latter part of the fifth coding period, and during this time the printing can be done in a leisurely manner.

A modification of the above construction is shown in Fig. 6. Here pin ll does not come out and engage with the abutment on the shaft. Instead it moves from position H6 into position ll when it penetrates into. the slots of the permutation bars, and in doing so it moves an auxiliary pin from position 38 to position 38, and in its latter position the auxiliary pin is capable of engaging with the proper abutment on the type wheel shaft. When this happens, pin ll, under the action of the knock-off plate l6, returns, as previously described, into its original condition of freedom from any connection with the permutation bars, H45, permitting the latter to move freely to the right (Fig. 1), and in due time pin 38 is returned into its own inoperative position by knock-off plate 3'1. The employment of the construction shown in Fig. 6 means that 32 additional pieces of mechanism have to be installed, as well as an additional cam and knockoif plate aggregate. On the other hand, it facilitates greatly the operation of the device. As stated above, with the apparatus shown in Figs. 1-3, it is necessary to set the shaft into rotation in the latter part of the fifth coding period, and to withdraw the pin from the slots not later than early in the first coding impulse, to make it possible to operate the first permutation bar H, which otherwise might have been immobilized by the'pin lying in its slot in that bar. The time for the operation is therefore very short. On the other hand, with the apparatus shown in Fig. 6, once the auxiliary bar has been moved from position 36 to 38 and is equipped with some form of detent to keep it in the latter position, the bar I! may be returned from position i! where it is in engagement in a slot in the permutation bars to position I'Efi where it is unengaged, Without affecting the position of auxiliary bar 38. The selection of locations of the permutation bars may therefore proceed without interference, and therefore more time may be devoted to rotating the type wheel shaft. The following brief calcu- 5 lation will show the importance of this feature. Let it be assumed that the printer has been designed to operate at '7 characters per second and that the spinning starts at the end of the fifth coding period and stops at the end of the stop period. Substantially, 40 milliseconds will be then available for the rotation of the type wheel shaft. With the arrangement shown in Fig. 6, the rotation may be continued until the latter part of the third period, printing and returning pin 38 to its original position on the fourth coding period, and giving for the turning of the type wheel shaft nearly five periods or close to 100 milliseconds. A 250 per cent increase in time available means a similar decrease in the speed of rotation, and, asthe impact of the abutment against the pin varies as the square of the speed, this means nearly a six times reduction in impact, a very valuable advantage in the way of reduction ill) Vii

ting shaft.

of the signaling impulses take place.

of noise and vibration, and "increase in life and reliability of the apparatus.

The operation of the apparatus requires the employment of several cams. One such cam has to control the motion of the permit plate or bar I6 operated at some time early in the'fifth coding period. Another cam controls the motion of the face member I24 taking place at the end of the stop period or very early in the first coding period with the arrangement shown in Figs. 1 and 2. It is assumed in all timing that the entire period is required for the performance of the operation appertaining thereto. In the case of the apparatus shown in Fig. 6, a cam is required to operate knock-off plate S'Ireturning pin 38 into its inoperative position 36. The stop "I29 is operated by the same cam as knock-off plate 31, the joint operation of the stop and pin 38 being as follows: To start with, knock off plate 3'! is in a position where it is in contact'with part 39 of pin 38 at which time pin Il occupies position H8. The latter rises to position Il under the action of its spring I8, Fig. 1, when the proper slots in the permutation bars become lined up, and in doing so, I! pushes 36 into position 38. While this is going on, knock-off plate 31 recedes to itsposition shown in Fig. 6 and in the lattermost part of its motion releases the stop I29 from its engagement Withratchet 128, thus permitting the type wheel shaft to start turning.

The following is quoted verbatim from the paper, Teleprinters, by E. S. Bitter, No. 150, in-

stitution of Post Ofiice Electrical Engineers, read March v28, 1933, p. 20: A point to notice in connection with reception is that evenwhen the transmitting teleprinter is running fast and the receiving teleprinter slow, the receiving shaft must be at a standstill when the following start signal comes in. If this is not so, there will be a loss of. margin on the signals. It follows there- .fore that the receiving shaft mustcomplete its revolution in a shorter time than the transmit- In the Creed 7A and 3A teleprinters the transmitting shaft makes one revolution for 7.5 signal elements and the receiving shaft one revolution for 7 elements. In the case of the Morkrum and Siemens machines the transmitting shaft makes one revolution for I-unit signals. The Morkrum instrument makes .one revolution in the time of about 6.5 signal units, and the Siemens in about the time of 6 units but with adelayed start of about half a unit,-so that in both cases the effective time of one revolution is 6.5 units. Where the receiving mechanism is brought to rest in 6.5 units there is a possibility of the instrument failing to stop if the fifth code element is late and also spacing polarity, but in this case the margin would be so small that probably the fourth and fifth code elements wouldfail to select correctly. The receiving shaft running faster than the transmitting shwftzs one of the essential features of a teleprinter. The italic is made by the present applicant.

This is illustrated in Fig. '7 taken fromthe paper just quoted, p. 19. The signal polarity (current to no-current and vice versa, positive to negative and vice versa) change must take place in the hatched portions for correct selection. As telegraph engineers know, there are many reasons why distortion and prolongation Theeffects of these disturbing phenomena are comparatively slight in the first, second and third coding periods asonlya magnet moving a stationary body has to be energized. The stop signal must, on

pressed.

the other hand, be sufiiciently active, in time as well as power, to operate an armature and stop a revolving shaft F, thus providing the necessary interval between F and Ed which latter is the beginning of the earliest next start signal. As the time is definitely fixed for the cycle by the time difference between the two consecutive start signals, which in turn is set by the speed of the machine, the only way to ensure the availability of a sufficient time for the performance of the stop operation is to carry through in less time the coding operations where a greater margin of safety is inherent.

All the telegraph printers now in use have.

solved the problem set forth above by the expedient of providing two shafts, transmitting and receiving, and running the latter faster than the former. E. S. Ritter, in the passage quoted above,

refers to this arrangement as one of the essen- The present intransmitting shaft'is running at the rate of 6.5

signal elements and the receiving shaft at 7 signal elements. The electrical circuit for the present invention is shown in Fig. 5 from which it is seen that the depression of key IIIcauses the downward motion of a keybar equipped with a code comb in the manner usual to this kind of telegraph printer, the comb being so arranged that it closes the electrical contacts determined by the code for the given character, plus a universal contact X operated for every character (this latter provision is also well known in the art). Let it be assumed that the letter Z is being transmitted and its code calls for a marking impulse during the first and fifth coding periods, and spacing during the rest. The depression of key II I causes the establishment of the following circuit, part of which is actual and part potential. The current starts from sending source of current I I 3 hereinafter referred to as battery and goes through contacts II4I and 4-5 which close when the keys IIII and I II-5 are de- It goes then through magnets II 6I and 6-5 which operatethe permutation bars of the receiver connected with the sender where such a combination apparatus has been provided. Where only a sender is provided, this step is of course absent. The current then goes to commutator SC having (for a five-unit code) seven segments, the respective contacts for Z involving segments III--I and Ill-5. Thence the current proceeds .to the receiving station by wire 40 where it enters commutator RC having likewise seven segments and running in a predetermined time relationship with the SC commutator. Thence the current goes through the proper magnets of the receiving apparatus and returns by ground or return loop indicated as II9R, I I9S, battery II3.

It should be noted here that where we have only a sender at one end and only a receiver at the other, there is no object in making the shaft of the same shaft and therefore run in perfect mechanical synchronism. The segments l5, and if desired, start, on the receiving commutator are slightly shorter, or rather embrace smaller angles, than on the transmitting commutator, the difference being determined by the desired difference in speed between the two shafts or by the desired accumulation of margin for the stop period. This is indicated in the table in Fig. 8.

If the transmitting shaft runs slower than the receiving shaft, or, if for two shafts running at the same speed the coding segments on the seven point sunflower commutator of the transmitting shaft are longer than those of the receiving shaft, or, if an equivalent structure is employed wherein both commutators in each apparatus are mounted on the same shaft and the respective shafts run at the same speed, the difference in timing of the early period such as starting and first-coding are very small, but this difference is of a cumulative character and becomes quite material in the latter impulses. Thus, as shown by table of Fig. 8, this difference is 1.5 milliseconds or about 3.9 degrees for the start impulse but becomes 7.5 milliseconds at the end of the fourth coding impulse. It would appear, therefore, that at the time when the fourth coding impulse has been concluded on the faster running receiver the transmitter has still 7.5 milliseconds to use in sending the fourth coding impulse. If no further precaution were taken, it might easily happen that the segment corresponding to the fifth coding impulse on the receiver would be in communication with the segment corresponding to the fourth coding impulse on the sender. In the present invention this might mean that the magnet actuating the trigger 22 on the fifth permutation bar might be operated by the impulse coming through the fourth segment on the sender, and it might easily happen that while the code calls for a spacing period on the fifth permutation bar, this premature superposition might produce the effect of a marking impulse during the fifth period with the attendant mis-transmission of a character.

This has been obviated in the present invention by the use of the auxiliary commutator 22 IR, located preferably in the line connecting the unsegmented part of the sending commutator SC of the sending station with the unsegmented part 'of the receiving commutator of the receiving station. This commutator consists of wheel G equipped with the proper number of projections, movable arm 136 preferably provided with bump l3! and contact I38 coacting where necessary with the stationary contact E39. No current is flowing through disc I35 which therefore if desired, can be made of a non-conducting material or mounted on a non-conducting hub. This commutator is mounted on the same shaft as all the other commutators driven through the singlerevoluticn clutch or associated therewith t rough some kind of a transmission. The contacts I38 and I39 carry the current of the circuit and are usually pressing against each other except as separated by the action of the bumps on the disc E35. The width of these bumps or cams determines the duration of the break of current between the contacts.

Commutator I35 is mounted on the same shaft as receiving commutator RC and performs two functions, one of which will be discussed later in connection with the sending auxiliary commutator 22 IS. This commutator 22 U3, however, has a very important function in that it prevents the possibility of premature operation of the magnets controlling the permutation bars of the receiver in the latter coding periods. The bumps such as I31 and l352 naturally have a certain minimum width, no cam having an instantaneous rise. Under normal conditions of operation this bump occupies about 10 degrees of the complete revolution, substantially half of which distance may be assigned to one period and the other half to the next adjacent period. This is sufficient for the early coding periods. It has been shown, however, that in the latter coding periods, as, e. g., at the end of the fourth, the phase difference between the proper segment of the receiving with the proper segment of the sending commutator may amount to as much as 7.5 out of 20 milliseconds which may be sufficient to cause trouble. To account for this, the width of the lump in the latter coding impulses may be increased to such an extent as to prevent the flow of current from the sender to the receiver, during the period when an excessive phase difference prevails, so that, e. g., the width of the bump may be made such as to occupy 16-18 degrees at the passage from the fourth to the fifth segment of the receiver as compared with, say, 10 degrees in the early coding impulses. It would be of course possible to make all the bumps of the maximum width, but this would unnecessarily cut into the margin of safety for the signals in the early impulses.

It is impossible to give a general formula for the proportioning of the bumps as this depends on the code selected and the difference of speed between the transmitting and receiving shafts, or, the equivalent to this difference as expressed by the difference of length between the coding seg ments of the receiver commutator RC and corresponding segments of the sending commutator SC.

It will be noted from Fig. 5 that the sending commutator SC is also equipped with an auxiliary commutator ZZIS. It is not necessary, however, to vary the width of the bumps on this commutator as it performs a function which does not need that particular refinement. Its purpose is as follows: When the brush of the sending commutator passes from one segment to another, particularly from a marking impulse to a spacing one, there is apt to be a spark between the arm of the commutator and the respective segment which if not taken care of will rapidly produce pitting and dirtying of the commutator segments. As the arm acts as a wiper over the face of the segments, it is rather difficult, mechanically, to take proper care of this spark. In commutator ZElS, however, the spark, if any, occurs between contact points 226 and 221, the contact between them being controlled by the bumps (general construction of commutator 22! S is similar to that of 221R). I-Iere, proper contacts can be easily installed and provision may be made so as to prevent any products of sparking from reaching the other parts of the machinery. To make commutator 22 IS operative it is necessary that the current should break through this commutator before it breaks across the space between the segments of commutator SC and that the circuit should be re-established at His later than it is re-established at SC. In this way both the make and the break sparking will take place at HIS and not at SC.

The above invention can be made operative only by ensuring a certain sequence of operations between its parts which has never been realized before. The cycle may be considered as starting with the energization or lack of energization of the magnets controlling the motion of the permutation bars, thus bringing about an alignment of the bars which provides a path for one pin to slide into a slot composed of five slot elements each located within one of the permutation bars. This is followed by a motion of the permit bar which is controlled by a cam located on the shaft driven by the single-revolution clutch or a shaft associated therewith and when this happens, the pin can actually slide into the slot which takes place preferably at some time in the fifth coding period, say about half Way from the begin-' ning of the period. The permit bar then continues to move and in doing so, causes the stop 129 to get out of engagement with the ratchet 128, and this starts the typewheel spinning. This should take place in the fifth coding period, as soon as possible after the projection of the pin into the slot and hence into the path of the abutments on the typewheel shaft. The permit bar then reverses its motion which is simultaneously slowed down, and in due time, which is to be as close to the end of the next start period as possible, returns the brake into engagement with the ratchet and then, not later than in the first part of the first coding period, knocks the pin out of the contact with the abutment and hence out of the slot in the permutation bars. The printing may then take place at any time between the first and the fifth coding periods for the next character, the typewheel in the meantime being held stationary by the stop.

The timing is somewhat different where the construction shown in Fig 6, with its auxiliary pins, is adopted. The preselector pin which means the one engaging with the slots in the permutation bars, still goes into the slot in the fifth period. By doing so it moves the auxiliary or selector pin into the path of the proper abutment. As soon as this has been done, the preselector pin may be returned into its original position without waiting for the engagement 'between the selector pin and the abutment on the shaft. The permit bar 16 may be moved into the position shown in Fig. 6 and a new cycle r of permutation bar selection may be initiated.

Pin 38 does not then have to engage with the abutment 102 until some time at the very end of the fourth coding period and may evenbe held until the beginning of the fifth coding period. The stop need not be set, unless otherwise desired, until some time in the fourth coding impulse which still leaves enough time for printing.

The general circuit is shown in Fig.5 for an apparatus having a receiver and sender combined. As usual in apparatus of this kind, the device prints the message sent. when acting as a sender as well as when acting as .a receiver. The position of switch Gill-602 determines the nature of the operation of the device. When the apparatus is acting as a sender, a key of a keyboard, not shown, is depressed which causes the closing of a. combination of switches selected from among the five, (l|4-l to HA5) which is usually done by a coding comb attached to the key lever. This part of the device is well known in the art. For the sakepfillustration let it be assumed that the depression of the key caused the closing of switch |l4-l. It also causes the opening of switch 4X which starts the apparatus going. When this happens the following circuit is established, with the switch 60| open and 602 closed: Battery H3 through 602 to the unsegmented ring of sunflower SC; over brush to segment I of SC, through magnet ll6--l to switch I M-I, closed, to commutator 226, out by 22'! and over the common to the line leading to the addressees apparatus indicated by ground 9S, and by wire!!! back to battery l l3. Magnet Ilfi-l is energized and causes the motion of the proper permutation bar which in. turn, in the manner set forth elsewhere in this applica-: tion causes the printing of a character or the actuation of a function.

To make the apparatus function as a receiver, a switch is moved which causes the opening of 6&2 and closing of GM, as well as closing of the switches 4B2l to 402 5, the switches ||4l to il. l5 naturally remaining open as the key.- boardis not eperated when the apparatus is used as a receiver. The currrent then fiows from the distant station acting as a transmitter from the right-hand side of battery H3 over the closed switch Sill and commutator ZZIR. to the unseg merited ring of sunflower BC, by brush to segment ill-A to magnet Hit-l, switch 402 to ground and wire 40'. When only two devices are connected with each other, as in the leased wire service, battery H3 maybe attached to either of the two devices or placed at some intermediary point between them. In suchservice as the British Telex, the battery or other source of current is usually locatedat the central. station. The location of battery H3 does not affect the circuit otherwise;

A modification of the circuit shown in Fig. 5 is presented inll lfig. 8. This involves the use of a double-throw eight-pole switch of a peculiar character. Here, as in Fig. 5, X-|, l|6l, etc. are the magnets operating the permutation bars. One side of these magnets is connected to the poles of the switch, second row from top, while the segments of the sender sunflower, SC, are connected to corresponding terminals of the switch, first row from the top. The segments of the receiver sunflower, RC, are connected to corresponding terminals of the switch on the other side of the pole line (third from the top). The com-.

mon line from the sender switch SS goes to commutator 22 IS and thence to battery I I3 while the individual lines from switch SS, such as ll4-- l (same'arrangement as in Fig. 5) are joined to the other-sides of the respective magnets by being hooked jointly into the proper terminals in the last row, from the top, of switch. When the machine is in the sending position, the switch is thrown towards the top of the sheet of the drawing connecting the first and second rows,counting from the top, and the following circuit, e. g. for H6 l, is established: Sender switch l4-I to terminal 2I4-| where the line from lM-l joins onto the line leading to magnet llG-l; through that magnet and to 2I6,l, i. e. to pole of the double-throw switch; thence, via switch pole, to terminal 3| 5 I connected to segment ,I of sunflower SC, by arm of the sunflower to the unsegmented ring and outof it to PS in the top row of terminals and-via the corresponding pole to battery H3; out of it to commutator ,22IS, and by the common wire back to sending switch lM-l.

The following circuit is established when the apparatus is acting as a receiver, it being assumedthat battery 3 is now located at the sender station. The switch is now thrown with the handle to the bottom of the drawing, connecting by the poles the second and third rows and the current is flowing from the bottom of battery H3 to pole P, thence to PR, commutator 22IR, unsegmented ring of sunflower RC, segment IHR, by pole to magnet ll6l; and

through the magnet I Hl to terminal 2l4--l. It will be noted that a bar CB, made of a conducting material, is provided, and joins toether all the terminals in the last row when the switch is in its receiver position, whilst 2 I 4-4 is joined to RS. The switch pole joins it to 19-2 which permits the current to flow to the other side of battery H3, and energizes magnet H6l in turn actuating the proper permutation bar.

I claim:

1. In a telegraph printer, a receiver comprising as many permutation bars as there are coding elements in the code used; a permit bar and means to actuate it subsequently to the periods available for the actuation of the permutation bars; selector elements and means to engage them with the selecting elements of the permutation bars; a shaft carrying the same number of abutments as there are selector ele-. ments, said abutments being so spaced with respect to the selector elements that only one selector element can engage with any of the abutments; a typewheel positioned on said shaft, together with means to lock and unlock said shaft; a cam and a source of energy to actuate it other than the signalling impulses, said cam being in a position to operate the means for locking and unlocking the typewheel shaft and being of such a shape as to unlock the typewheel shaft subsequently to the actuation of the permit bar.

2. Apparatus as set forth in claim 1 wherein the cam operating the permit bar is so shaped that the permit bar in one position of the cam constitutes a means to withhold the selector elements from coacting with the selecting elements; in its next position the cam is a means to move the permit bar into a position wherein it does not interfere with the coaction between the selector and selecting elements, and in the next following position the cam becomes a means to withdraw the selector elements from coacting with the abutments on the typewheel shaft.

3. Apparatus as set forth in claim 1 wherein the selector elements consist of two members whereof one is in a position to engage with the selecting elements of the permutation bars, said member thereby becoming the means to move the second member of the selector elements into a position of coacting with the corresponding abutments on the typewheel shaft, together with means to hold the second member of the selector in its operating position after the withdrawal of the first member from coaction with the permutation bars.

4. Apparatus as set forth in claim 1 wherein the selector elements consist of two members whereof one is in a position to engage with the selecting elements of the permutation bars, said member thereby becoming the means to move the second member of the selector elements into a position of coacting with the corresponding abutments on the typewheel shaft together with means to hold the second member of the selector in its operating position after the withdrawal of the first member from coaction with the permutation bars, and wherein further the permit bar provides a path for the first element of the selector to engage with the permutation bars in the latter part of the fifth coding, and disengages said selector element before the end of the next following fourth coding period.

5. Apparatus as set forth in claim 1 wherein the selector elements consist of two members whereof one is in a position to engage with the selecting elements of the permutation bars, said member thereby becoming the means to move the second member of the selector elements into a position of coacting with the corresponding abutments on the typewheel shaft, together with means to hold the second member of the selector in its operating position after the withdrawal of the first member from coaction with the permutation bars, but means are provided for return of said second element into its original inoperative position between the end of the first coding period and the end of the fourth coding period.

6. In a telegraph printer, a receiver and a sender each comprising a sunflower having two more units than there are time-units in the code for which the apparatus is constructed, the two last coding segments in the receiver sunflower being shorter than the corresponding segments in the sender sunflower, and the stop segment in the receiver sunflower longer than the corresponding segment in the sender sunflower, together with means to drive both sunflowers at the same angular velocity.

7. In an apparatus as set forth in claim 6, an interrupter in series with the receiver sunflower to break the fiow of current through the sunflower at the end of the fourth impulse during the period when the brush in the sending sunflower is on the fourth coding segment and in the receiving sunflower on the fifth coding segment.

8. Apparatus as set forth in claim 1 wherein the cam controlling the means to lock the typewheel shaft is so shaped that the shaft remains in its locked position until after the printing of the character set up by the coding impulses,

9. In a telegraph printer, a receiver com' prising as many permutation bars as there are coding elements in the code used; a permit bar and means to actuate it subsequently to the periods available for the actuation of the permutation bars; selector elements and means to engage them with the selecting elements of the permutation bars; a shaft carrying the same number of abutments as there are selector elements, said abutments being so spaced with respect to the selector elements that only one selector element can engage with any of the abutments; a typewheel positioned on said shaft, together with means to lock and unlock the shaft; a cam and a source of energy to actuate it other than the signalling impulses, said cam being in a position to operate the means for locking and unlocking the typewheel shaft and being of such a shape as to lock the typewheel shaft before the elapse of substantially one quarter of the time period assigned for the first coding period of the character next following.

LEON CAMMEN. 

